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Abstract:

To establish an alternative path without giving an influence on signal
continuity to a data transmission line to which a communication bandwidth
cannot be secured any more when the transmission capacity decreased by
adaptive modulation.
It includes a first radio node means which sets an adaptive modulation
changeover margin having a predetermined width to communication quality
for a trigger of performing adaptive modulation which decreases a
communication bandwidth when the communication quality of a radio
transmission channel section has deteriorated, and prior to performing
the adaptive modulation, in the adaptive modulation changeover margin,
instructs an initiator node which has established an LSP in the radio
transmission channel section to reserve a bandwidth of an alternative LSP
for the LSP which requires restoration of diverting to an alternative
path and to change over to the alternative LSP; and a second radio node
means which is the initiator node, and according to the instructions from
the first radio node means, reserves a bandwidth of the alternative LSP,
performs changeover to the alternative LSP and disconnects the LSP which
has been changed over to the alternative LSP.

Claims:

1-15. (canceled)

16. A bandwidth guaranteed system comprising: a first radio node unit,
configuring an MPLS (MULTI PROTOCOL LABEL SWITCHING) network, that sets
an adaptive modulation changeover margin having a predetermined width to
communication quality for a trigger of performing adaptive modulation
which decreases a communication bandwidth when the communication quality
of a radio transmission channel section has deteriorated, and prior to
performing the adaptive modulation, in the adaptive modulation changeover
margin, instructs an initiator node which has established an LSP (Label
Switched Path) in the radio transmission channel section to reserve a
bandwidth of an alternative LSP for the LSP which requires restoration of
diverting to an alternative path and to change over to the alternative
LSP; and a second radio node unit, configuring the MPLS network, that is
the initiator node, and according to the instructions from the first
radio node unit, reserves a bandwidth of the alternative LSP, performs
changeover to the alternative LSP and disconnects the LSP which has been
changed over to the alternative LSP.

17. The bandwidth guaranteed system according to claim 16, wherein the
adaptive modulation changeover margin comprises, a first threshold value
which is used for discriminating the LSP which requires the restoration
among the LSPs being established in the radio transmission channel
section, and becomes a trigger of instructing the second radio node unit
to reserve a bandwidth of the alternative LSP, a second threshold value
which indicates more deteriorated state of the communication quality than
the first threshold value, and instructs the second radio node unit to
perform changeover to the alternative LSP for which a bandwidth has been
reserved, and a third threshold value which indicates more deteriorated
state of the communication quality than the second threshold value, and
becomes a trigger of performing the adaptive modulation and decreasing a
communication bandwidth of the radio transmission channel section.

18. The bandwidth guaranteed system according to claim 17, wherein the
adaptive modulation changeover margin further comprises a fourth
threshold value which indicates improved state of the communication
quality more than the first threshold value, and wherein the first radio
node unit, when having detected the fourth threshold value without
detecting the second threshold value after detected the first threshold
value, instructs the second radio node unit to cancel bandwidth
reservation for the alternative LSP which was instructed at the time of
detecting the first threshold value.

19. The bandwidth guaranteed system according to claim 17, wherein the
first radio node unit, when having detected the first threshold value,
discriminates the LSP, for which a communication bandwidth cannot be
secured any more in a case where a communication bandwidth of the radio
transmission channel section decreased by the adaptive modulation, based
on the communication bandwidth required for respective LSPs being
established in the radio transmission channel section and the priority
set to the respective LSPs.

20. A radio node device comprising: a radio section state monitoring unit
that monitors communication quality of a radio transmission channel
section, and outputs communication quality status information; an
adaptive modulation control unit that performs adaptive modulation which
decreases a communication bandwidth of the radio transmission channel
section when the communication quality status information outputted by
the radio section state monitoring unit has reached an adaptive
modulation threshold value for a trigger of performing the adaptive
modulation set in advance; and a restoration control unit that when the
communication quality status information outputted by the radio section
state monitoring unit has reached a predetermined threshold value before
reaching the adaptive modulation threshold value, instructs an initiator
node which has established an LSP (Label Switched Path) of an MPLS (MULTI
PROTOCOL LABEL SWITCHING) network in the radio transmission channel
section to reserve a bandwidth of an alternative LSP for the LSP which
requires restoration of diverting to an alternative path and to change
over to the alternative LSP.

21. The radio node device according to claim 20, wherein the restoration
control unit, when discriminating the communication quality status
information has reached a predetermined first threshold value,
discriminates an LSP which requires the restoration among the LSPs being
established in the radio transmission channel section, and instructs the
initiator node to reserve a bandwidth of the alternative path, and when
discriminating the communication quality status information has reached a
second threshold value which indicates further deteriorated state more
than the first threshold value, instructs the initiator node to perform
changeover to the alternative LSP for which a bandwidth has been
reserved.

22. The radio node device according to claim 21, wherein the restoration
control unit, when discriminating the communication quality status
information has reached a predetermined improved threshold value, which
indicates improved state more than the first threshold value, without
reaching the second threshold value, after discriminating that the
communication quality status information has reached the predetermined
first threshold value, instructs the initiator node to cancel bandwidth
reservation for the alternative LSP which was instructed at the time of
discriminating that the first threshold value was reached.

23. The radio node device according to claim 21, wherein the restoration
control unit, when discriminating the communication quality status
information has reached the first threshold value, discriminates the LSP,
for which a communication bandwidth cannot be secured any more in a case
where a communication bandwidth of the radio transmission channel section
decreased by the adaptive modulation, based on the communication
bandwidth required for respective LSPs established in the radio
transmission channel section and the priority set to the respective LSPs.

24. The radio node device according to claim 22, wherein the restoration
control unit comprises, a threshold judging control unit that
discriminates any one of the first threshold value, the second threshold
value and the improved threshold value based on the communication quality
status information outputted by the radio section state monitoring unit;
a restoration list creating unit that, when the threshold judging control
unit has discriminated the first threshold value, discriminates an LSP
which requires the restoration among the LSPs established in the radio
transmission channel section and outputs first notification information
to instruct the initiator node to reserve a bandwidth of the alternative
LSP, and when the threshold judging control unit has discriminated the
second threshold value, outputs second notification information to
instruct the initiator node to perform changeover to the alternative LSP
for which a bandwidth has been reserved; and a notification information
transmission control unit that transmits the first notification
information or the second notification information outputted from the
restoration list creating unit to the initiator node.

25. The radio node device according to claim 24, wherein the restoration
list creating unit, when the threshold judging control unit has
discriminated the improved threshold value without discriminating the
second threshold value after having discriminated the first threshold
value, outputs third notification information to instruct the initiator
node to cancel bandwidth reservation for the alternative LSP which was
instructed by the first notification information, and wherein the
notification information transmission control unit transmits the third
notification information outputted by the restoration list creating unit
to the initiator node.

26. The radio node device according to claim 25, wherein the restoration
list creating unit, when the threshold judging control unit has
discriminated the first threshold value, discriminates the LSP, for which
a communication bandwidth cannot be secured any more in a case where a
communication bandwidth of the radio transmission channel section
decreased by the adaptive modulation, based on the communication
bandwidth required for respective LSPs established in the radio
transmission channel section and the priority set to the respective LSPs,
and creates a restoration list which registers as the LSP requiring the
restoration.

27. A bandwidth guaranteeing method in an MPLS (MULTI PROTOCOL LABEL
SWITCHING) network adopting adaptive modulation, comprising the steps of:
setting an adaptive modulation changeover margin having a predetermined
width to communication quality of a radio transmission channel section;
prior to performing the adaptive modulation, in the adaptive modulation
changeover margin, according to a deterioration condition of the
communication quality, reserving a bandwidth of an alternative LSP (Label
Switched Path) for establishing an alternative path by restoration for an
LSP being established in the radio transmission channel section; and
continuing communication by performing changeover to the alternative path
using the alternative LSP.

28. The bandwidth guaranteeing method according to claim 27, further
comprising the steps of: discriminating an LSP which requires the
restoration among the LSPs established in the radio transmission channel
section and instructing the initiator node to reserve a bandwidth of the
alternative path, when the communication quality has reached a
predetermined first threshold value in the adaptive modulation changeover
margin; and instructing the initiator node to perform changeover to the
alternative LSP for which a bandwidth has been reserved, when the
communication quality has reached a second threshold value which
indicates further deteriorated state more than the first threshold value.

29. The bandwidth guaranteeing method according to claim 28, further
comprising: instructing the initiator node to cancel bandwidth
reservation for the alternative LSP which was instructed at the time of
reaching the first threshold value in a case where after the
communication quality has reached the predetermined first threshold
value, and has reached a predetermined improved threshold value which
indicates improved state more than the first threshold value without
reaching the second threshold value.

30. The bandwidth guaranteeing method according to claim 28, further
comprising: discriminating the LSP, for which a communication bandwidth
cannot be secured any more in a case where a communication bandwidth of
the radio transmission channel section decreased by the adaptive
modulation, based on the communication bandwidth required for respective
LSPs established in the radio transmission channel section and the
priority set to the respective LSPs, when the communication quality
having reached the first threshold value.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a bandwidth guaranteed system, a
radio node device and a bandwidth guaranteeing method, particularly to a
bandwidth guaranteed system, a radio node device and a bandwidth
guaranteeing method in an MPLS (MULTI PROTOCOL LABEL SWITCHING) network
which is composed of the radio node devices adopting adaptive modulation.

BACKGROUND ART

[0002] A radio system using microwaves (in particular, quasi-millimeter
wave band), which tends to be influenced by rainfall attenuation, adopts
adaptive type coding/modulation (henceforth, referred to as adaptive
modulation) for the purpose of improvement of availability of radio
links. Adaptive modulation is a technique which enables wide band and
stable radio communication using radio waves as the communication medium
influenced by external causes. And, adaptive modulation is technology
which varies a modulation method according to a change in the propagation
environment of radio waves, for example, fluctuation of bit error rate.
Adaptive modulation can suppress increase of the error rate by performing
low bit rate modulation at time of deteriorated condition of the
propagation environment and avoid deterioration of the communication
quality from being occurred. Adaptive modulation can make the
transmission rate high by performing high bit rate modulation at time of
good condition of the propagation environment.

[0003] As the modulation methods, there are BPSK (Binary Phase Shift
Keying), QPSK (Quadrature Phase Shift Keying) and 16 QAM (16 Quadrature
Amplitude Modulation) or the like. The number of bits that can be
transmitted per one symbol in each modulation method is 1 bit in case of
BPSK, 2 bits in case of QPSK and 4 bits in case of 16 QAM. And, the bit
error rate characteristics in each modulation method deteriorate in the
order of BPSK, QPSK and 16 QAM.

[0004] Accordingly, when the propagation environment of radio waves is
bad, BPSK and QPSK which are the modulation methods having strong error
tolerance are used. Further, when the propagation environment of radio
waves is good, it gives priority to the transmission rate over the error
tolerance, and for example, 16 QAM which indicates the double
transmission rate of QPSK is used for the modulation method.

[0005] On the other hand, there is MPLS as technology for composing a
network.

[0006] MPLS is technology which has introduced a concept of a label in
order to realize flexible path control which is free from a framework of
layer 3 in the network which is composed of routers. In other words, MPLS
is technology which attaches a label to a place located in the middle of
a data link header of layer 2 and an IP (Internet Protocol) packet header
of layer 3, and transmits packets at high speed based on information
included in the label. Therefore, MPLS can realize routing of packets
which is not constrained by an IP address.

[0007] The traffic between edge nodes of MPLS is transmitted using a
connection, called a label path (henceforth, referred to as LSP: Label
Switched Path), which is a fixed path. Therefore, it can be said that
MPLS has introduced connection-oriented mechanism into an IP network
which is connectionless. And, MPLS can explicitly establish and control a
path having an idle bandwidth more than a requested bandwidth using a
signaling protocol in each link through which this LSP passes. As the
signaling protocol, there is CR-LDP (Constraint-based Routed Label
Distribution Protocol) and RSVP-TE (Resource Reservation Protocol Traffic
Engineering) or the like. In other words, in MPLS, the technology which
effectively uses bandwidth resources of the whole network and guarantees
communication quality is specified.

[0008] MPLS calculates a path which is capable of providing a required
bandwidth for communication using a path calculation algorithm which
takes constraints of an available bandwidth or the like into account. The
path obtained in this way is reserved in each of routers prior to
performing communication. That is, the bandwidth corresponding to the
path is secured in each of routers. As a result, the quality of
communication is guaranteed and the bandwidth resources of the network
are used more effectively.

[0009] The bandwidth control technology which controls a communication
bandwidth while suppressing influence given to the communication in a
communication system which is constructed by connecting radio devices
corresponding to adaptive modulation and MPLS routers is disclosed in
patent document 1 (Japanese Patent Application Publication No.
2006-287549). This technology solves such a problem that the data, which
should be able to be transmitted with a reserved bandwidth, cannot be
transmitted actually due to decrease of a communication bandwidth by
adaptive modulation if adaptive modulation by the radio device is
performed regardless of the communication bandwidth being reserved on the
MPLS router.

[0010] The MPLS router disclosed in patent document 1 searches for an
alternative path to which a communication path corresponding to the
decreased amount of the communication bandwidth is to be diverted, when
notification of a change in the modulation method to a low order is
received from the radio device. And, when having found the alternative
path, the MPLS router changes the modulation method in the original radio
circuit while using the alternative path. Even if not found an
alternative path, the modulation method is changed after performing
disconnection of the communication path. In other words, when performing
the change in the modulation method to a low order, when having found the
alternative path, communication of the communication path which cannot be
accommodated anymore due to the change in the modulation method to a low
order is maintained via other adjacent MPLS routers. Also, even if not
found an alternative path, it controls the communication bandwidth while
suppressing influence given to the communication by performing release
processing first to the communication path which cannot be accommodated
any more due to the change in the modulation method to a low order.

[0011] Patent document 2 (domestic re-publication of PCT international
publication for patent applications WO 2006001308) discloses a radio link
system which can reconfigure a path depending on fluctuation of the
bandwidth which occurs in association with a change in the propagation
environment of the radio link. In this system, an arbitrary radio node
device among a plurality of radio node devices detects the transmission
state of its own radio link that is connected to itself, and changes the
modulation method of the radio link based on the detected transmission
state of the radio link. And, this radio node device transmits
information indicating the changed modulation method and the number of
paths using the radio link in which the modulation method has been
changed to a path control device. The path control device detects a path
which requires a path change based on the information indicating the
modulation method and the number of paths using the radio link in which
the modulation method has been changed transmitted from the radio node
device, and determines a new path from the state of the whole radio
links.

[0012] Further, an MPLS network has a restoration function which
calculates an alternative path for fault relief to a fault occurring in
the MPLS network and performs processing for establishing a new LSP. In
the MPLS network, when a fault has occurred in a link which an LSP uses,
information about the fault event is notified to an initiator node of the
LSP. A Notify message of RSVP (Resource Reservation Protocol) is used for
this notification, and by this, the fault event is notified directly from
a node of the fault section to the initiator node which performs the
fault relief. The initiator node which has received the Notify message
calculates the alternative path and newly establishes an LSP. The fault
relief processing method of MPLS network like this is disclosed in patent
document 3 (Japanese Patent Application Publication No. 2005-333383).

[0013] Technology which patent document 3 discloses eliminates a
possibility that a different path included in the fault section is
selected as the alternative path, and it enables to perform the fault
relief processing stably. According to this technology, when a fault has
occurred at any path of the MPLS network, the Notify message which is
fault event information is transmitted from a node which has detected the
fault. When the Notify message is received, the node which performs the
fault relief begins to measure protection time by using this reception as
a trigger. During this protection time, LSA (Link State Advertisement) of
a routing protocol of OSPF (Open Shortest Path First) is collected. When
the protection time is completed, the node which performs the fault
relief executes alternative path calculation based on the Notify message
and LSA of OSPF, and performs the fault relief by performing the
restoration processing.

[0018] In a radio system adopting adaptive modulation, the transmission
capacity and the communication quality are contrary elements each other.
When the transmission capacity is increased, the error tolerance becomes
low and the communication quality deteriorates. On the other hand, when
the transmission capacity is decreased, the error tolerance becomes high
and it improves the communication quality. Therefore, when attenuation of
microwaves caused by a change in the weather has occurred, control is
performed so as to secure the required communication quality and improve
the error tolerance by decreasing the transmission capacity.

[0019] It will be described specifically with reference to FIGS. 12 to 14.

[0020]FIG. 12 is a network composed of radio node devices 1101-1106 which
adopt adaptive modulation. A transmission line via the radio node device
1103 is established to the radio node device 1106 from the radio node
device 1101. As the transmission line, a high priority data transmission
line L101 and a low priority data transmission line L102 are established
using VLAN (Virtual Local Area Network) and QoS (Quality of Service) or
the like. Users transmit and receive communication data through these two
kinds of data transmission lines.

[0021] When attenuation of microwaves has occurred due to a change in the
weather or the like in the section (W104) between the radio node device
1103 and the radio node device 1105, each of the radio node devices 1103
and 1105 decreases the transmission capacity in order to secure the
required communication quality.

[0022] FIG. 13 is a schematic diagram illustrating a problem when
decreasing the transmission capacity as a result of adaptive modulation.
FIG. 13(a) indicates the state of the data transmission line between the
radio node device 1103 and the radio node device 1105 before adaptive
modulation is performed, and FIG. 13(b) indicates the state of the data
transmission line after performing adaptive modulation. In FIG. 13(a),
communication bandwidths of both of the high priority data transmission
line L101 and the low priority data transmission line L102 are secured.
However, when adaptive modulation which decreases the transmission
capacity is performed in order to secure the required communication
quality in association with deterioration of the propagation environment,
the communication bandwidths of both of the high priority data
transmission line L101 and the low priority data transmission line L102
cannot be secured any more. Therefore, QoS control which preferentially
secures a communication bandwidth of the high priority data transmission
line L101 is performed. As a result, as shown in FIG. 13(b), the
communication bandwidth of the low priority data transmission line L102
cannot be secured any more, and the data transmission line L102 is
disconnected and the communication cannot be performed any more.

[0023] In the technology disclosed in patent document 1, an MPLS router
searches for an alternative path to which the communication path
corresponding to the decreased amount of the communication bandwidth is
to be diverted, when notification of the change in the modulation method
to a low order is received from the radio device. And communication of
the communication path which cannot be accommodated any more is
maintained via the alternative path.

[0024] Further, in the technology disclosed in patent document 2, with
respect to fluctuation of the bandwidth which occurs in association with
the change in the propagation environment of the radio link, information
indicating a modulation method and the number of paths using the radio
link in which the modulation method has been changed is transmitted to
the path control device. The path control device detects a path which
requires a path change based on the information, and determines a new
path from the state of the whole radio links.

[0025] However, the technology disclosed in patent document 1 searches for
an alternative path and performs changeover to the alternative path after
having received the notice of change in the modulation method from a
radio device. Also, the technology disclosed in patent document 2,
similarly after having received the notice about radio link in which the
modulation method has been changed, is performing control for detecting a
path required for a required path change for it.

[0026] Accordingly, in both of the technology disclosed in patent document
1 and the technology disclosed in patent document 2, some data are
discarded during a period from decreasing transmission capacity by
adaptive modulation actually being performed to changeover traffics to
the alternative path.

[0027]FIG. 14 is an explanation drawing showing the state that
discontinuity of the data transmission line occurs in establishing the
alternative path in this way.

[0028] This means that there is a problem that the risk of frequent
occurrence of data discarding in a low priority data transmission line
becomes high, because adaptive modulation operation is frequently
performed in such a case where the propagation environment of the radio
wave changes frequently due to frequent occurrences of the change in the
weather or the like.

[0029] The object of the present invention is to provide a bandwidth
guaranteed system, a radio node device and a bandwidth guaranteeing
method which solve the above-mentioned problem, and can establish an
alternative path without giving an influence on signal continuity for a
data transmission line for which a communication bandwidth cannot be
secured any more due to decrease in transmission capacity by adaptive
modulation.

Solution to Problem

[0030] In order to realize the above-mentioned object, a bandwidth
guaranteed system according to the present invention is characterized by
including, a first radio node means, configuring an MPLS (MULTI PROTOCOL
LABEL SWITCHING) network, which sets an adaptive modulation changeover
margin having a predetermined width to communication quality for a
trigger of performing adaptive modulation which decreases a communication
bandwidth when the communication quality of a radio transmission channel
section has deteriorated, and prior to performing the adaptive
modulation, in the adaptive modulation changeover margin, instructs an
initiator node which has established an LSP (Label Switched Path) in the
radio transmission channel section to reserve a bandwidth of an
alternative LSP for the LSP which requires restoration of diverting to an
alternative path and to change over to the alternative LSP; and a second
radio node means, configuring the MPLS network, which is the initiator
node, and according to the instructions from the first radio node means,
reserves a bandwidth of the alternative LSP, performs changeover to the
alternative LSP and disconnects the LSP which has been changed over to
the alternative LSP.

[0031] Further, a radio node device according to the present invention is
characterized by including, a radio section state monitoring means which
monitors communication quality of a radio transmission channel section,
and outputs communication quality status information; an adaptive
modulation control means which performs adaptive modulation which
decreases a communication bandwidth of the radio transmission channel
section when the communication quality status information outputted by
the radio section state monitoring means has reached an adaptive
modulation threshold value which is set in advance and becomes a trigger
of performing the adaptive modulation; and a restoration control means
which when the communication quality status information outputted by the
radio section state monitoring means has reached a predetermined
threshold value before reaching the adaptive modulation threshold value,
instructs an initiator node which has established an LSP (Label Switched
Path) of an MPLS (MULTI PROTOCOL LABEL SWITCHING) network in the radio
transmission channel section to reserve a bandwidth of an alternative LSP
for the LSP which requires restoration of diverting to an alternative
path and to change over to the alternative LSP.

[0032] Further more, a bandwidth guaranteeing method in an MPLS network
adopting adaptive modulation according to the present invention is
characterized by including, setting an adaptive modulation changeover
margin having a predetermined width to communication quality of a radio
transmission channel section; prior to performing the adaptive
modulation, in the adaptive modulation changeover margin, according to a
deterioration condition of the communication quality, reserving a
bandwidth of an alternative LSP for establishing an alternative path by
restoration to an LSP being established in the radio transmission channel
section; and continuing communication by performing changeover to the
alternative path using the alternative LSP.

Advantageous Effects of Invention

[0033] The present invention can establish an alternative path without
giving an influence on signal continuity for a data transmission line for
which a communication bandwidth cannot be secured any more, even when the
transmission capacity has decreased by performing adaptive modulation in
association with deterioration of the propagation environment of the
radio transmission channel section.

BRIEF DESCRIPTION OF DRAWINGS

[0034]FIG. 1 is a system configuration drawing showing a basic exemplary
embodiment of the present invention.

[0035] FIG. 2 is a system configuration drawing showing an MPLS network
including radio node devices corresponding to adaptive modulation in an
exemplary embodiment of the present invention.

[0036]FIG. 3 is a system configuration drawing showing the state that an
alternative LSP is established by a restoration function of MPLS.

[0037]FIG. 4 is a block diagram showing a main configuration of the radio
node device corresponding to adaptive modulation according to the
exemplary embodiment of the present invention.

[0038]FIG. 5 is a block diagram showing a configuration of a restoration
control unit of the radio node device.

[0039]FIG. 6 is an explanation drawing showing a relation among various
threshold values used in the exemplary embodiment of the present
invention.

[0040]FIG. 7 is a flow chart showing an outline of operation of the
restoration control unit.

[0042]FIG. 9 is a flow chart showing operation of the radio node device
according to the exemplary embodiment of the present invention.

[0043] FIG. 10 is an explanation drawing which visually indicates an
effect of the exemplary embodiment of the present invention.

[0044]FIG. 11 is another explanation drawing which visually indicates an
effect of the exemplary embodiment of the present invention.

[0045]FIG. 12 is an explanation drawing which explains a problem to be
solved by the invention, and is a system configuration drawing
illustrating a premise system.

[0046] FIG. 13 is an explanation drawing which explains a problem to be
solved by the invention, and is a schematic diagram illustrating a
problem when performing adaptive modulation and decreasing the
transmission capacity.

[0047]FIG. 14 is an explanation drawing which explains a problem to be
solved by the invention, and is a drawing showing the state that
discontinuity of the data transmission line occurs in establishing the
alternative path.

DESCRIPTION OF EMBODIMENTS

[0048]FIG. 1 is a system configuration drawing showing a basic exemplary
embodiment for realizing a bandwidth guaranteed system of the present
invention.

[0049] A bandwidth guaranteed system of a basic exemplary embodiment
according to the present invention sets an adaptive modulation changeover
margin having a predetermined width to communication quality which
becomes a trigger of performing adaptive modulation which decreases a
communication bandwidth when the communication quality of a radio
transmission channel section has deteriorated. And, a first radio node
device 11 and a second radio node device 12 configure the MPLS network.
The first radio node means 11, prior to performing the adaptive
modulation, in the adaptive modulation changeover margin, instructs an
initiator node which has established an LSP in the radio transmission
channel section to reserve a bandwidth of an alternative LSP for the LSP
which requires restoration of diverting to an alternative path and to
change over to the alternative LSP. The second radio node means 12, that
is the above-mentioned initiator node, according to the instructions from
the first radio node means, reserves a bandwidth of the alternative LSP,
performs changeover to the alternative LSP and disconnects the LSP which
has been changed over to the alternative LSP.

[0050] A bandwidth guaranteeing method of this basic exemplary embodiment
is a bandwidth guaranteeing method in the MPLS network adopting adaptive
modulation, and sets an adaptive modulation changeover margin having a
predetermined width to communication quality of a radio transmission
channel section. And, prior to performing the adaptive modulation, in the
adaptive modulation changeover margin, according to a deterioration
condition of the communication quality, performs the following
processing. Firstly, it reserves a bandwidth of an alternative LSP for
establishing an alternative path by restoration for an LSP being
established in the radio transmission channel section. Then, it continues
communication by performing changeover to the alternative path using the
alternative LSP.

[0051] Here, the restoration is processing or function performed by a node
device configuring the MPLS network which calculates an alternative path
for a fault occurred in the MPLS network and newly establishes an LSP for
the fault relief.

[0052] The basic exemplary embodiment of the present invention sets the
adaptive modulation changeover margin to the communication quality that
becomes a trigger of performing the adaptive modulation. And, it performs
the restoration by the processing during this changeover margin.
Therefore, it is possible to perform changeover a path without giving an
influence on signal continuity because it can divert a path to the
alternative LSP before the bandwidth capacity of the transmission line
decreases.

[0053] The exemplary embodiment of the present invention will be further
described with reference to drawings.

[0054] FIG. 2 is a system configuration drawing of the exemplary
embodiment according to the present invention showing an MPLS network
which is composed on radio node devices 101-106 adopting adaptive
modulation. An LSP as a data transmission line via the radio node devices
102, 103 and 105 is established to the radio node device 106 which is a
terminator node (Terminator) from the radio node device 101 which is an
initiator node (Initiator). A high priority data transmission line P101
and a low priority data transmission line P102 are established in the LSP
using VLAN and QoS or the like. Users transmit and receive communication
data through these two kinds of data transmission lines.

[0055] Each radio node device performs the label switching and the traffic
management based on the specification of MPLS. Further, each radio node
device monitors fluctuation or the like of the bit error rate in
respective radio links W101-W106 between each of adjacent radio node
devices, and performs adaptive modulation which makes the modulation
multiple value number increase or decrease according to a change in the
propagation environment of the radio waves.

[0056]FIG. 3 is a system configuration drawing showing the state that an
alternative LSP is established by a restoration function of MPLS.

[0057] It indicates the situation that a change in the propagation
environment of the radio waves occurs due to rainfall in the radio link
W104 of the MPLS network shown in FIG. 2, and the radio node device 103
and the radio node device 105 perform adaptive modulation.

[0058] When an LSP exists for which a communication bandwidth cannot be
secured any more by performing adaptive modulation, the radio node device
103 transmits a Notify message to the initiator node which has
established the LSP, and instructs to perform the restoration for
performing fault relief. The radio node device 101 which is the initiator
node of the LSP calculates an alternative path for the fault relief, and
newly establishes the data transmission line P105 as an alternative LSP.

[0059] Further, although the radio node device 105 which is opposite to
the radio node device 103 performs the same processing as the radio node
device 103 to an LSP in an opposite direction which is not illustrated,
for the sake of making explanation simple, only processing for the LSP in
the illustrated direction will be described.

[0060] In this exemplary embodiment, the present invention has a feature
in control operation performed by the radio node device 103, which
monitors the state of the radio link W104, according to the change in the
propagation environment before actually performing adaptive modulation.
Description will be made later of this control operation.

[0061]FIG. 4 is a block diagram showing a main configuration of the radio
node device 100 corresponding to adaptive modulation according to the
exemplary embodiment of the present invention. Further, the radio node
device 100 is a device which represents the first radio node means 11 and
the second radio node means 12 shown in FIG. 1, and the radio node
devices 101-106 shown in FIG. 2 and FIG. 3.

[0062] The radio node device 100 is configured by including a radio
section status monitoring unit 110, an adaptive modulation control unit
120 and a restoration control unit 130.

[0063] The radio section status monitoring unit 110 monitors the
communication quality of the radio transmission channel section and
outputs communication quality status information. In other words, the
radio section status monitoring unit 110 has a function to monitor the
propagation state of radio waves which is the transmission line state in
the radio transmission channel section managed by this radio node device
100. The propagation state of radio waves is judged, for example, using
the bit error rate. The radio section status monitoring unit 110 detects
the bit error rate, and may output only the value of this bit error rate.
Also, the radio section status monitoring unit 110 discriminates whether
the transmission line state has exceeded the various threshold values
that will be mentioned later or not based on the detected bit error rate
value, and when exceeding the respective threshold values, it may output
corresponding information which indicates that it has exceeded the
respective threshold values.

[0064] The adaptive modulation control unit 120 has a function to control
adaptive modulation by a modulation method corresponding to the change in
state of the radio transmission channel section based on the information
outputted by the radio section status monitoring unit 110. When the
communication quality status information outputted by the radio section
status monitoring unit 110 has reached a predetermined adaptive
modulation threshold value which becomes a trigger of performing adaptive
modulation which decreases a communication bandwidth of the radio
transmission channel section, the adaptive modulation control unit 120
performs the adaptive modulation.

[0065] The restoration control unit 130 has a function to perform
restoration control according to the transmission line state in the radio
transmission channel section based on the information outputted by the
radio section status monitoring unit 110. When the communication quality
status information outputted by the radio section status monitoring unit
110 has reached a predetermined threshold value which is a value before
reaching the adaptive modulation threshold value, the restoration control
unit 130 performs the restoration control. As will be mentioned later,
for an LSP which requires the restoration among the LSPs of MPLS network
established in the radio transmission channel section, the restoration
control unit 130 instructs the initiator node of the LSP to reserve a
bandwidth of an alternative LSP and to perform changeover to the
alternative LSP successively.

[0066]FIG. 5 is a block diagram showing a configuration of the
restoration control unit 130 of the radio node device 100. The
restoration control unit 130 is configured by including a threshold
judging control unit 131, a restoration list creation unit 132 and a
Notify transmission control unit 133.

[0067] The threshold judging control unit 131 has a function to
discriminate in what state the transmission line state in the radio
transmission channel section is based on the information outputted by the
radio section status monitoring unit 110. And, the threshold judging
control unit 131 discriminates the transmission line state which becomes
a trigger of various kinds of control, and outputs information
corresponding to the discriminated state.

[0068] The restoration list creation unit 132 has a function to create a
restoration list and a stay list which will be mentioned later based on
the information outputted by the threshold judging control unit 131. The
restoration list creation unit 132 outputs information relating to the
LSP which is an object of fault relief based on the created restoration
list.

[0069] Further, the restoration list is a list which registers an object
LSP of restoration when a communication bandwidth of the radio
transmission channel section has decreased by adaptive modulation.
Further, the stay list is a list which registers an object LSP which
continues its communication as it is even if a communication bandwidth of
the radio transmission channel section has decreased by adaptive
modulation.

[0070] The Notify transmission control unit 133 has a function to perform
control for transmitting a Notify message to an initiator node which has
established the object LSP of fault relief based on the information
outputted by the threshold judging control unit 131 and the information
outputted by the restoration list creation unit 132.

[0071] Operation of the exemplary embodiment of the present invention in
the system configuration and the device configuration described above
will be described in detail with reference to FIGS. 6 to 9.

[0072]FIG. 6 is an explanation drawing showing a relation of a first
threshold value to a fourth threshold value used in the exemplary
embodiment of the present invention for discriminating the state of the
radio transmission channel section.

[0073] The first threshold value is a threshold value (the pre-restoration
threshold value) for performing evacuation preparation of an LSP, for
which a communication bandwidth cannot be secured any more when adaptive
modulation is performed, by reserving a bandwidth of an alternative LSP
for the LSP.

[0074] The second threshold value is a threshold value (the restoration
threshold value) for performing actual restoration which makes a path
divert to the alternative LSP for which a bandwidth has been reserved.

[0075] The third threshold value is a threshold value (the adaptive
modulation threshold value) for actually performing adaptive modulation
which decreases a communication bandwidth of the radio transmission
channel section.

[0076] The fourth threshold value is a threshold value (the restoration
cancellation threshold value) for canceling the alternative LSP for which
a bandwidth has been reserved when the transmission line state is
improved after performing bandwidth reservation by detection of the
pre-restoration threshold value.

[0077] The margin between the pre-restoration threshold value and the
adaptive modulation threshold value is called an adaptive modulation
changeover margin.

[0078] Referring to FIG. 6, when the pre-restoration threshold value A is
detected, the radio node device 100 calculates whether the restoration of
LSP is needed or not taking a bandwidth required for the LSP currently
being established and the priority order into account before decreasing a
communication bandwidth by performing adaptive modulation. When the
restoration of LSP is needed, it transmits a Notify message to the
initiator node of the LSP and instructs to perform bandwidth reservation
for an alternative LSP.

[0079] Next, the radio node device 100 which has detected the restoration
threshold value B instructs the initiator node, to which bandwidth
reservation for the alternative LSP was instructed, to execute the
restoration for making a path divert to the alternative LSP. As a result,
the original LSP for which the restoration to alternative LSP has been
performed is disconnected.

[0080] Further next, the radio node device 100 which has detected the
adaptive modulation threshold value C performs adaptive modulation and
decreases a communication bandwidth of the radio transmission channel
section.

[0081] On the other hand, referring to FIG. 6, the radio node device 100
which has detected the restoration cancellation threshold value D1 after
detecting the pre-restoration threshold value A1 because of the
transmission line state improvement instructs the initiator node, to
which bandwidth reservation for the alternative LSP was instructed, to
cancel the restoration.

[0082] Further, referring to FIG. 6, the radio node device 100, which had
detected the pre-restoration threshold value A2, and further detected the
restoration threshold value B2, instructs the initiator node of LSP to
reserve a bandwidth of the alternative LSP and to execute the
restoration. Therefore, the LSP used to be the object has already been
disconnected, and data communication is performed by having diverted a
path to the alternative LSP. Accordingly, the radio node device 100 does
not perform anything, even if the transmission line state improves and
the restoration cancellation threshold value D2 is detected after such
state.

[0083] Further, the radio section status monitoring unit 110 may judge
these threshold values by holding corresponding information on the value
of the bit error rate and each threshold value in the radio section
status monitoring unit 110. Further, only with the radio section status
monitoring unit 110 outputting the value of the detected bit error rate,
the restoration control unit 130 and the adaptive modulation control unit
120 may discriminate the threshold value required for each control. In
the latter case, the restoration control unit 130 and the adaptive
modulation control unit 120 hold corresponding information on the value
of the bit error rate and each required threshold values.

[0084]FIG. 7 is a flow chart showing the outline of operation of a
restoration control unit 130.

[0085] The threshold judging control unit 131 of the restoration control
unit 130 discriminates the transmission line state in the radio
transmission channel section based on the information outputted by the
radio section status monitoring unit 110, and when having detected the
pre-restoration threshold value, this triggers commencement of the
control operation.

[0086] Operation of Step S701 will be described. The threshold judging
control unit 131 instructs the restoration list creation unit 132, when
having detected the pre-restoration threshold value, to create a
restoration list. Also, the threshold judging control unit 131 notifies
the Notify transmission control unit 133 of the effect that the
pre-restoration threshold value has been detected.

[0087] As will be described in detail later, the restoration list creation
unit 132 creates the restoration list by confirming existence of the LSP
which becomes an object of restoration taking a bandwidth required for
the LSP currently being established and the priority order into account.
When the object LSP of restoration exists, the restoration list creation
unit 132 instructs the Notify transmission control unit 133 to transmit a
Notify message. At this time, the restoration list creation unit 132
notifies the Notify transmission control unit 133 of LSP information
including an LSP identifier of the object LSP which exists in the
restoration list.

[0088] The Notify transmission control unit 133 transmits the Notify
message to the initiator node of the LSP based on the detection
information of the pre-restoration threshold value notified from the
threshold judging control unit 131 and the LSP information notified from
the restoration list creation unit 132. The Notify message transmitted at
that time instructs bandwidth reservation for an alternative LSP.

[0089] Next, operation of Step S702 will be described.

[0090] Step S702 is an operation in a case where the threshold judging
control unit 131 is discriminating the transmission line state in the
radio transmission channel section based on information continuously
outputted by the radio section status monitoring unit 110, and has
detected the restoration threshold value.

[0091] The threshold judging control unit 131 notifies the restoration
list creation unit 132 and the Notify transmission control unit 133 of
the effect that it has detected the restoration threshold value,
respectively.

[0092] The restoration list creation unit 132 notifies the Notify
transmission control unit 133 of LSP information of the LSP which exists
in the restoration list and becomes an object of restoration.

[0093] The Notify transmission control unit 133 transmits the Notify
message to the initiator node of the LSP based on the detection
information of the restoration threshold value notified from the
threshold judging control unit 131 and the LSP information notified from
the restoration list creation unit 132. The Notify message transmitted at
this time instructs execution of the restoration to the alternative LSP.

[0094] Next, operation of Step S703 will be described. Step S703 is an
operation in a case where the threshold judging control unit 131 detects
the restoration cancellation threshold value after execution of
controlling Step S701 by detecting the pre-restoration threshold value.
In other words, operation of Step S703 is carried out when improvement of
the transmission line state of the radio transmission channel section is
discriminated in the discrimination operation of the transmission line
state in the radio transmission channel section which is continuously
being performed based on outputted information by the radio section
status monitoring unit 110.

[0095] The threshold judging control unit 131 notifies the restoration
list creation unit 132 and the Notify transmission control unit 133 of
the effect that it has detected the restoration cancellation threshold
value.

[0096] The restoration list creation unit 132 notifies the Notify
transmission control unit 133 of LSP information of the LSP which exists
in the restoration list and is to be an object of restoration.

[0097] The Notify transmission control unit 133 transmits the Notify
message to the initiator node of the LSP based on the detection
information of the restoration cancellation threshold value notified from
the threshold judging control unit 131 and the LSP information notified
from the restoration list creation unit 132. The Notify message
transmitted at this time instructs cancellation of bandwidth reservation
for the alternative LSP instructed in Step S701.

[0098] Step S704 is an operation in a case where improvement of the
transmission line state in the radio transmission channel section is
discriminated after execution of the restoration by detecting the
restoration threshold value.

[0099] The restoration was performed in Step S702, and the LSP used to be
the object was diverted to the alternative LSP by the initiator node, and
the original LSP has already been disconnected. Therefore, even if the
restoration cancellation threshold value is detected, no control
operation is performed.

[0100] Also, in this case, the threshold judging control unit 131 notifies
the restoration list creation unit 132 and the Notify transmission
control unit 133 of the effect that it has detected the restoration
cancellation threshold value.

[0101] Because the restoration list creation unit 132 can discriminate
that the restoration has already been performed, it ignores this
detection notification of the restoration cancellation threshold value.

[0102] Further, while the Notify transmission control unit 133 receives
the notice of detection of the restoration cancellation threshold value
from the threshold judging control unit 131, it ignores this detection
notification of the restoration cancellation threshold value because it
does not receive information from the restoration list creation unit 132.

[0103] Performing as above, the restoration control unit 130 controls the
restoration according to the transmission line state in the radio
transmission channel section based on the information outputted by the
radio section status monitoring unit 110.

[0104] Further, although the above-mentioned description is based on the
configuration of the restoration control unit 130 shown in FIG. 5, it
does not need to operate as these necessarily. For example, the threshold
judging control unit 131 may notify only the restoration list creation
unit 132 of the discrimination information on the threshold value, and
the restoration list creation unit 132 may notify the Notify transmission
control unit 133 of information which instructs the control operation to
be performed.

[0105] In this case, the restoration list creation unit 132 which has
received the detection notice of the pre-restoration threshold value
creates the restoration list first. Then, the restoration list creation
unit 132 instructs the Notify message transmission control unit 133 to
transmit the Notify message, together with the LSP information existing
there, to instruct bandwidth reservation for the alternative LSP.

[0106] Further, the restoration list creation unit 132 which has received
the detection notice of the restoration threshold value instructs the
Notify message transmission control unit 133 to transmit the Notify
message, together with the LSP information of the object, to instruct
execution of the restoration to the alternative LSP.

[0107] Further, the restoration list creation unit 132 which has received
the detection notice of the restoration cancellation threshold value
discriminates whether it had received the detection notice of the
restoration threshold value or not. When it had not received the
detection notice of the restoration threshold value, the restoration list
creation unit 132 instructs the Notify message transmission control unit
133 to transmit the Notify message to instruct cancellation of bandwidth
reservation for the alternative LSP. When it had received the detection
notice of the restoration threshold value, the restoration list creation
unit 132 ignores this detection notification of the restoration
cancellation threshold value.

[0108] Further, the initiator node (the radio node device 101 of FIG. 3)
which was instructed bandwidth reservation for the alternative LSP in the
operation of above-mentioned Step S701 performs alternative path
calculation to the terminator node (the radio node device 106 of FIG. 3)
based on the network of current state when it receives the Notify
message. In that case, the initiator node (the radio node device 101)
performs the path calculation by excluding (exclusion) the path including
the radio transmission channel section (W104 of FIG. 3) which is subject
to be notified by the Notify message. By the above process, a section
whose bandwidth capacity has decreased may not be selected again. The
initiator node (the radio node device 101 of FIG. 3) performs bandwidth
reservation for the alternative LSP (P105 of FIG. 3) based on the result
of the path calculation. When the bandwidth reservation for the
alternative LSP is failed, the initiator node searches for another
alternative path again and performs re-establishment of a different
alternative LSP.

[0109]FIG. 8 is a flow chart showing operation relating to creation on
the restoration list executed in the restoration list creation unit 132.

[0110] The restoration list creation unit 132 starts this operation by
receiving the detection notice of the pre-restoration threshold value
from the threshold judging control unit 131.

[0111] The restoration list creation unit 132 creates a stay list and a
restoration list taking a bandwidth required for the LSP currently being
established and the priority order into account. The stay list is a list
which registers an object LSP which continues its communication as it is
even if a communication bandwidth of the radio transmission channel
section has decreased by adaptive modulation. Further, the restoration
list is a list which registers an object LSP of restoration when a
communication bandwidth of the radio transmission channel section has
decreased by adaptive modulation. The restoration list includes LSP
information which includes a LSP identifier of the object LSP and a flag
or the like which shows yes or no indication of reservation execution for
the alternative LSP based on detection of the pre-restoration threshold
value.

[0112] The operation of Steps S801 to S803 is a sort processing which
rearranges the order of the LSPs currently being established in
accordance with the priority order and the use bandwidth order. By this
processing, the processing to confirm existence of the LSP which is the
object of restoration is successively performed from the LSP having high
priority and using wide bandwidth.

[0113] Operation after Step S804 will be described for each step.

[0114] Step S804 extracts one piece of information on the LSP, among the
LSPs currently being established, which is using wide bandwidth by high
priority of the first order as a result of the above-mentioned sort
processing.

[0115] Step S805 checks the magnitude correlation between the remaining
transmission line bandwidth capacity which is the decreased bandwidth
capacity after executing adaptive modulation and the bandwidth to be used
by this LSP.

[0116] When the remaining transmission line bandwidth capacity is larger
or equivalent in this check, the transmission capacity of the LSP can be
maintained (YES of S805) even if a communication bandwidth of the radio
section decreased by execution of adaptive modulation. Therefore, this
LSP is registered to the stay list. When the LSP is registered to the
stay list, the bandwidth capacity to be used by this LSP is subtracted
from the remaining transmission line bandwidth capacity, and the
remaining transmission line bandwidth capacity is updated (S806).

[0117] On the other hand, as a result of the check of Step S805, when the
remaining transmission line bandwidth capacity is smaller, the
transmission capacity of the LSP cannot be maintained any more (NO of
S805) when a communication bandwidth of the radio transmission channel
section decreases by execution of adaptive modulation. Therefore, this
LSP is made the object of restoration and registered to the restoration
list (S807). It is not necessary to update the remaining transmission
line bandwidth capacity when the LSP is registered to the restoration
list.

[0118] Step S808 judges whether the remaining transmission line bandwidth
capacity updated in Step S806 is still left or not. When the remaining
transmission line bandwidth capacity is still left by this judgment (NO
of S808), it judges in Step S809 whether the assigning processing to the
stay list or the restoration list mentioned above is completed or not for
the LSPs currently being established.

[0119] When the above-mentioned processing to all LSPs currently being
established is not completed (exist of S809), it returns to Step S804,
extracts one piece of information on the LSP using wide bandwidth by high
priority of the next order, and Steps S805 to S809 mentioned above are
repeated. Further, when the above-mentioned processing to all LSPs
currently being established has been completed (not exist of S809), it
ends this restoration list creation processing.

[0120] On the other hand, as a result of the judgment of Step S808, when
the remaining transmission line bandwidth capacity updated in Step S806
is no longer left (YES of S808), the following processing is performed.
It is judged in Step S810 whether the assigning processing to the stay
list or the restoration list mentioned above is completed or not for the
LSPs currently being established.

[0121] When the above-mentioned processing to all LSPs currently being
established is not completed (exist of S810), all the remaining LSPs are
registered to the restoration list (S811). In other words, it is because
the transmission capacity for all remaining LSPs cannot be maintained any
more due to no remaining transmission line bandwidth capacity.

[0122] Further, when the above-mentioned processing to all LSPs currently
being established has been completed (not exist of S810), it ends this
restoration list creation processing.

[0123] Performing as above, the restoration list creation unit 132 creates
the stay list and the restoration list taking a bandwidth required to the
LSP currently being established and the priority order into account.

[0124] Operation of the radio node device according to the exemplary
embodiment of the present invention will be described with reference to
FIG. 9 based on the contents described above.

[0125]FIG. 9 is a flow chart showing operation of the radio node device
according to the exemplary embodiment of the present invention.

[0126] As has been described in FIG. 4, the radio section status
monitoring unit 110 monitors the transmission line state in the radio
transmission channel section in the radio node device 100 (S901). And,
the restoration control unit 130 judges the execution necessity of
restoration based on the information outputted by the radio section
status monitoring unit 110. In other words, the restoration control unit
130 judges whether the state of the radio transmission channel section
deteriorates or not more than the pre-restoration threshold value
described in FIG. 6 (S902).

[0127] In the judgment of Step S902, when it is discriminated that the
state of the radio section has deteriorated more than the pre-restoration
threshold value (YES of S902), the restoration control unit 130 creates
the stay list and the restoration list by the operation described in FIG.
8 (S903). In the restoration list, the LSP for which a communication
bandwidth cannot be secured any more when a communication bandwidth of
the radio transmission channel section decreased by adaptive modulation
and which becomes the object of restoration is registered.

[0128] However, as a result of the restoration list creation processing of
Step S903, even if a communication bandwidth of the radio transmission
channel section decreased by adaptive modulation, in a case where the
communication bandwidth for all LSPs currently being established can be
secured, none of the LSPs is registered to the restoration list. In other
words, in this case, all LSPs are registered to the stay list.

[0129] Accordingly, in the judgment of Step S904, when there is no
registration LSP in the restoration list (not exist of S904), the
restoration control unit 130 ends the processing without performing any
more processing. On the other hand, in the judgment of Step S904, when
the registered LSPs exist in the restoration list (exist of S904), the
restoration control unit 130 transmits the Notify message to instruct
bandwidth reservation for the alternative LSP to the initiator node of
each registered LSP (S905).

[0130] The initiator node which has received the Notify message to
instruct bandwidth reservation for the alternative LSP performs
calculation of the alternative path to a terminator node from the present
network. In that case, the initiator node performs the path calculation
by excluding (exclusion) the path including the radio transmission
channel section which is subject to be notified by the Notify message. As
a result, it is arranged so that the section, in which the bandwidth
capacity having decreased, may not be selected again. The initiator node
performs bandwidth reservation for the alternative LSP based on the
result of the path calculation. When the bandwidth reservation for the
alternative LSP is failed, the initiator node searches for another
alternative path again and performs re-establishment of a different
alternative LSP.

[0131] After that, the radio section status monitoring unit 110 continues
to monitor the state of the radio transmission channel section (S906).
And, the restoration control unit 130 discriminates whether the state of
the radio transmission channel section deteriorates more than the
restoration threshold value described in FIG. 6 based on the information
outputted by the radio section status monitoring unit 110 (S907).

[0132] In the judgment of Step S907, when the state of the radio
transmission channel section does not deteriorate more than the
restoration threshold value (NO of S907), it discriminates whether the
state of the radio transmission channel section improves or not more than
the restoration cancellation threshold value described in FIG. 6 (S912).
And, when discriminating that it is improved more than the restoration
cancellation threshold value (YES of S912), the restoration control unit
130 transmits the Notify message to instruct reservation cancellation of
the alternative LSP bandwidth to the initiator node to which reservation
of the alternative LSP bandwidth was instructed in Step S905 (S913). The
initiator node which has received the Notify message to instruct
reservation cancellation of this alternative LSP bandwidth cancels the
alternative LSP for which a bandwidth has been reserved.

[0133] On the other hand, when it is discriminated that the state of the
radio section does not improve more than the restoration cancellation
threshold value (NO of S912), the processing returns to Step S906.

[0134] Further, in the judgment of Step S907, when it is discriminated
that the state of the radio transmission channel section has deteriorated
more than the restoration threshold value (YES of S907), it transmits the
Notify message to instruct the restoration to the alternative LSP to the
initiator node to which reservation of the alternative LSP bandwidth was
instructed in Step S905 (S908). The initiator node which has received the
Notify message to instruct this restoration to the alternative LSP
diverts a path to the alternative LSP. And, it performs deletion of the
original LSP of the restoration.

[0135] At this stage, adaptive modulation in the radio transmission
channel section is not performed yet. However, diverting a path to the
alternative LSP is performed at this stage for the LSP for which a
bandwidth cannot be secured when a communication bandwidth decreased by
adaptive modulation.

[0136] The state of the radio transmission channel section is monitored
continually (S909), and it is discriminated whether the state of the
radio transmission channel section deteriorates or not more than the
adaptive modulation threshold value described in FIG. 6 based on the
information outputted by the radio section status monitoring unit 110
(S910). This discrimination is performed by the adaptive modulation
control unit 120. Further, the radio section status monitoring unit 110
may discriminate and notify the adaptive modulation control unit 120.

[0137] The judgment processing of Step S914 is processing in a case where
the state of the radio transmission channel section does not deteriorate
more than the adaptive modulation threshold value in the judgment of Step
S910 (NO of S910).

[0138] In a case where the state of the radio transmission channel section
is worse than the restoration threshold value but does not deteriorate
more than the adaptive modulation threshold value, it is continually
monitored whether the state of the radio transmission channel section
deteriorates or not more than the adaptive modulation threshold value (NO
of S914, S909, S910).

[0139] Further, in a case where the state of the radio transmission
channel section is improved without reaching the adaptive modulation
threshold value, and it is improved at least more than the restoration
threshold value, the processing ends without adaptive modulation being
performed (YES of S914). In other words, in the situation that the state
of the radio transmission channel section is improved, this radio node
device does not need to perform anything, because the restoration was
performed in Step S908 and the restoration object LSP has already
performed path diversion to the alternative LSP.

[0140] In the judgment of Step S910, when discriminating that the state of
the radio section deteriorated more than the adaptive modulation
threshold value (YES of S910), the adaptive modulation control unit 120
instructs the radio control device which is not illustrated to perform
adaptive modulation (S911).

[0141] By the above, the radio node device 100 ends its processing.

[0142] Thus, the radio node device 100 of this exemplary embodiment
prepares the restoration at time when the state of the radio transmission
channel section deteriorates and it has reached the pre-restoration
threshold value. In other words, the LSP which becomes the object of
restoration is sorted out taking the bandwidth capacity required for the
LSP currently being established and the priority order into account.
Reservation of the alternative LSP is instructed to the initiator node of
the object LSP of restoration. And, at time when the state of the radio
transmission channel section further deteriorates and has reached the
restoration threshold value, the radio node device instructs execution of
restoration. However, because the radio node device has not performed
adaptive modulation yet as of this, there is no change in a communication
bandwidth in the radio transmission channel section. Adaptive modulation
is performed at time when the state of the radio transmission channel
section further deteriorates and has reached the adaptive modulation
threshold value.

[0143] FIG. 10 and FIG. 11 are explanation drawings which visually
indicate an effect by this exemplary embodiment.

[0144] FIG. 10 shows each state that it reserves a bandwidth of the
alternative LSP (P105) for the LSP (P102) at time when the state of the
radio section has reached the pre-restoration threshold value, and it
performs path diversion to the alternative LSP (P105) at time when having
reached the restoration threshold value and disconnects the original LSP
(P102). Accordingly, because communication using the alternative path by
the alternative LSP (P105) is being performed at time when a
communication bandwidth decreased by performing adaptive modulation due
to the state of the radio section having reached the adaptive modulation
threshold value, it can eliminate the transmission line disconnecting
time and realize the bandwidth guarantee of End to End.

[0145] In FIG. 11, FIG. 11 (a) shows the state of the radio transmission
channel section of the usual state, and FIG. 11 (b) shows the state of
the radio transmission channel section after adaptive modulation is
performed, respectively.

[0146] As has been described above, the bandwidth guaranteed system of the
present invention sets the adaptive modulation changeover margin having a
predetermined width to communication quality which becomes a trigger of
performing the adaptive modulation which decreases a communication
bandwidth when the communication quality of the radio transmission
channel section has deteriorated. And, prior to performing the adaptive
modulation based on the communication quality status in the adaptive
modulation changeover margin, it makes path diversion to the alternative
LSP perform by discriminating the LSP to which fault relief is to be
applied. Therefore, the bandwidth guaranteed system of the present
invention can guarantee the bandwidth to the LSP of all priority order by
performing the restoration which diverts a path to the alternative LSP
even in a case where a communication bandwidth decreased by adaptive
modulation. Further, even when it makes the path diversion to the
alternative LSP perform, it is possible to divert a path to the
alternative path without having an influence on signal continuity.

[0147] While the invention has been particularly shown and described with
reference to exemplary embodiments thereof, the invention is not limited
to these embodiments. It will be understood by those of ordinary skill in
the art that various changes in form and details may be made therein
without departing from the spirit and scope of the present invention as
defined by the claims.

[0148] This application is based upon and claims the benefit of priority
from Japanese patent application No. 2010-000352, filed on Jan. 5, 2010,
the disclosure of which is incorporated herein in its entirety by
reference.

INDUSTRIAL APPLICABILITY

[0149] The present invention can be used in a communication system which
is configured by connecting radio devices and MPLS (MULTI PROTOCOL LABEL
SWITCHING) routers.